Most venomous snakes on Earth lack a specific antivenom. With more than 600 venomous snake species worldwide, only a fraction have a dedicated treatment designed to neutralize their venom. Some of these gaps exist because the snakes rarely bite humans, but others involve species that kill people regularly in regions where antivenom production simply isn’t economically viable.
Why So Many Species Lack Antivenom
Making antivenom is expensive and complicated. The process requires maintaining live venomous snakes, extracting their venom, injecting small amounts into horses or sheep to produce antibodies, then purifying those antibodies into a usable product. Every step costs money: animal husbandry, manufacturing, quality control, cold-chain storage, and distribution. The final product has a limited shelf life and must be refrigerated, which creates additional challenges in tropical regions where snakebites are most common.
For a manufacturer to justify that investment, there needs to be enough demand. Many venomous species bite so few people, or live in such remote areas, that no company can sell enough antivenom to turn a profit. When Sanofi-Pasteur discontinued its Fav-Afrique antivenom, which covered multiple African snake species, the company cited limited profits and market failure as the reasons. That single decision left large parts of sub-Saharan Africa with fewer treatment options overnight. The WHO classified snakebite envenoming as a highest-priority neglected tropical disease in 2017, partly in response to these kinds of gaps.
Snakes With No Antivenom at All
Several medically significant snakes have zero commercially available antivenom. These are species whose bites can cause serious injury or death, yet hospitals have nothing specific to offer victims.
Twig snakes (Thelotornis species): Found across sub-Saharan Africa, twig snakes are rear-fanged colubrids with potent venom that causes uncontrollable bleeding. Their venom triggers consumption coagulopathy, meaning it uses up the body’s clotting factors so blood can no longer clot normally. Victims experience spontaneous bleeding from the gums, gut, and even the brain. Despite the severity of these bites, no antivenom is manufactured for any Thelotornis species. The famous herpetologist Karl Schmidt died from a twig snake bite in 1957, and the treatment situation hasn’t fundamentally changed since.
Asian keelback snakes (Rhabdophis species): These snakes are widespread across Asia, and their bites can cause serious bleeding disorders. Japan produces an antivenom for one species, the yamakagashi (Rhabdophis tigrinus), but it is scarce even within Japan and is not exported. For the rest of the genus, including the red-necked keelback found across Southeast Asia, no antivenom exists. Because these snakes range across many countries with large rural populations, this gap affects millions of people living in potential bite zones.
Many African vipers and cobras: Numerous species in Africa, particularly less-common vipers and spitting cobras, have no species-specific antivenom. Polyvalent antivenoms (designed to cover multiple species) exist for some of the most medically important African snakes, but their coverage is incomplete. Species outside the “big four” or “big five” of a given region often fall through the cracks entirely.
Snakes With Critically Limited Antivenom
Some species technically have an antivenom, but supply is so fragile that it may as well not exist for many patients.
Eastern coral snake (Micrurus fulvius): The only antivenom licensed in the United States for coral snake bites comes from a single manufacturing lot originally produced by Wyeth Pharmaceuticals, now owned by Pfizer. The FDA has repeatedly extended the expiration date on this lot, most recently pushing it to June 30, 2025. No alternative product is licensed in the U.S. for coral snake envenomation. This means the entire country’s coral snake treatment depends on a dwindling stockpile of a product that is no longer being manufactured. A Mexican product called Coralmyn exists but isn’t FDA-approved for routine use in American hospitals.
Boomslang (Dispholidus typus): The boomslang is another rear-fanged colubrid, native to sub-Saharan Africa, with venom that causes severe bleeding. South Africa’s Vaccine Producers (SAVP) is the only manufacturer of a monovalent boomslang antivenom. Production was interrupted for a period, and the next batch is expected for release at the end of November 2025. Outside of southern Africa, this antivenom is essentially unobtainable. Zoos in other countries that keep boomslangs sometimes maintain a small emergency supply, but a bite victim in a region without pre-stocked antivenom faces a serious problem.
What Happens When No Antivenom Exists
When someone is bitten by a snake that has no antivenom, doctors rely entirely on supportive care. The specifics depend on what the venom does to the body.
For venoms that cause paralysis, the priority is keeping the patient breathing. This can mean manual resuscitation or mechanical ventilation for hours or even days until the venom’s effects wear off. For venoms that disrupt blood clotting, patients may need transfusions of blood products and careful monitoring for internal bleeding, particularly bleeding into the brain. Kidney damage is another common consequence of certain venoms. Some patients require long-term dialysis, and in severe cases, kidney transplantation.
Local tissue destruction is harder to manage without antivenom. Venom that destroys tissue at the bite site can lead to extensive wound care, reconstructive surgery, and in the worst cases, amputation. The WHO notes that comprehensive rehabilitation services are a necessary part of snakebite treatment, reflecting the reality that many survivors face lasting disability.
Polyvalent Antivenoms Fill Some Gaps
One strategy for covering more species is polyvalent antivenom, which is made by immunizing animals against venom from multiple snake species at once. Australia’s antivenom system is a good example. Testing has shown that Australian monovalent antivenoms actually contain antibodies that bind to venoms from multiple species, making them functionally polyvalent. This means a tiger snake antivenom, for instance, offers some cross-protection against other Australian elapid venoms.
The limitation of polyvalent products is that broader coverage often means lower potency against any individual species. Larger doses may be needed, which drives up cost and increases the risk of allergic reactions. For regions with dozens of medically important species, like West Africa or Southeast Asia, designing a polyvalent antivenom that adequately covers the most dangerous local snakes is a significant scientific and economic challenge.
The Species That Matter Most
From a practical standpoint, the snakes most people should know about are the ones in their own region. If you live in or travel to the southeastern United States, the coral snake antivenom situation is worth being aware of. In sub-Saharan Africa, boomslang and twig snake bites are medical emergencies with extremely limited treatment options. Across South and Southeast Asia, keelback snakes and various kraits and vipers present risks that local healthcare systems may not be equipped to handle.
The broader picture is sobering. An estimated 5.4 million snakebites occur worldwide each year, and the majority happen in tropical developing countries where antivenom access is worst. For many of the 600-plus venomous species, no specific antivenom has ever been developed, and the economic realities of manufacturing make it unlikely that most of these gaps will close anytime soon. The snakes that do have antivenom are, in many ways, the exceptions.